Polyaxial bone anchor with compound articulation and pop-on shank

ABSTRACT

A polyaxial bone screw assembly includes a threaded shank body having an integral shank head receivable in a one-piece receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A compression insert (some with an independent tool lock, lock and release feature and/or friction fit feature) and a split retaining ring articulatable with respect to both the shank head and the receiver (prior to locking) cooperate with the receiver to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. Ser. No.61/465,812, filed Mar. 24, 2011 and incorporated by reference herein.This application is also a continuation-in-part of U.S. patentapplication Ser. No. 13/373,289 filed Nov. 9, 2011 that claims thebenefit of U.S. Prov. Pat. App. Ser. No. 61/456,649 filed Nov. 10, 2010and U.S. Prov. Pat. App. Ser. No. 61/460,234 filed Dec. 29, 2010, all ofwhich are incorporated by reference herein. This application is also acontinuation-in-part of U.S. patent application Ser. No. 12/924,802filed Oct. 5, 2010 that claims the benefit of the following U.S. Prov.Pat. App. Ser. Nos.: 61/278,240, filed Oct. 5, 2009; 61/336,911, filedJan. 28, 2010; 61/343,737 filed May 3, 2010; 61/395,564 filed May 14,2010; 61/395,752 filed May 17, 2010; 61/396,390 filed May 26, 2010;61/398,807 filed Jul. 1, 2010; 61/400,504 filed Jul. 28, 2010;61/402,959 filed Sep. 8, 2010; 61/403,696 filed Sep. 20, 2010; and61/403,915 filed Sep. 23, 2010, all of which are incorporated byreference herein. This application is also a continuation-in-part ofU.S. patent application Ser. No. 12/072,354 filed Feb. 26, 2008 thatclaims the benefit of U.S. Prov. Pat. App. Ser. No. 60/905,472 filedMar. 7, 2007 and is a continuation-in-part of U.S. patent applicationSer. No. 11/126,965 filed May 10, 2005, now U.S. Pat. No. 7,476,239 andis a continuation-in-part of U.S. patent application Ser. No. 12/008,067filed Jan. 8, 2008, now U.S. Pat. No. 7,901,437, that claims the benefitof U.S. Prov. App. Ser. No. 60/897,723 filed Jan. 26, 2007, all of whichare incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone screws for use inbone surgery, particularly spinal surgery and particularly to suchscrews with compression or pressure inserts and expansion-only splitretainers to snap over, capture and retain the bone screw shank head inthe receiver member assembly and later fix the bone screw shank withrespect to the receiver assembly.

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. Although bothclosed-ended and open-ended bone screws are known, open-ended screws areparticularly well suited for connections to rods and connector arms,because such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw. Generally, the screws must be insertedinto the bone as an integral unit along with the head, or as apreassembled unit in the form of a shank and pivotal receiver, such as apolyaxial bone screw assembly.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke with a U-shapedslot or channel to receive a rod. Hooks and other types of connectors,as are used in spinal fixation techniques, may also include similar openends for receiving rods or portions of other fixation and stabilizationstructure.

A common approach for providing vertebral column support is to implantbone screws into certain bones which then in turn support a longitudinalstructure such as a rod, or are supported by such a rod. Bone screws ofthis type may have a fixed head or receiver relative to a shank thereof,or may be of a polyaxial screw nature. In the fixed bone screws, the rodreceiver head cannot be moved relative to the shank and the rod must befavorably positioned in order for it to be placed within the receiverhead. This is sometimes very difficult or impossible to do. Therefore,polyaxial bone screws are commonly preferred. Also, it is oftendesirable to insert the bone screw shank separate from the receiver orhead due to its bulk which can get in the way of what the surgeon needsto do. Such screws that allow for this capability are sometimes referredto as modular polyaxial screws.

With specific reference to modular snap-on or pop-on polyaxial pediclescrew systems having shank receiver assemblies, the prior art has shownand taught the concept of the receiver and certain retainer partsforming an assembly wherein a contractile locking engagement between theparts is created to fix the shank head with respect to the receiver andretainer. The receiver and shank head retainer assemblies in the priorart have included a slotted contractile retainer ring and/or a lowerpressure slotted insert with an expansion and contraction collet-type ofstructure having contractile locking engagement for the shank head dueto direct contact between the retainer and/or the collet structure withthe receiver resulting in contraction of the slotted retainer ringand/or the collet-type structure of the insert against the shank head.The receiver and slotted insert have generally included tapered lockingengagement surfaces.

The prior art for modular polyaxial screw assemblies has also shown andtaught that the contact surfaces on the outside of the slotted colletand/or retainer and the inside of the receiver, in addition to beingtapered, can be conical, radiused, spherical, curvate, multi-curvate,rounded, as well as other configurations to create a contractile type oflocking engagement for the shank head with respect to the receiver.

In addition, the prior art for modular polyaxial screw assemblies hasshown and taught that the shank head can both enter and escape from acollet-like structure on the insert or from the retainer when the insertor retainer is in the up position and within an expansion recess orchamber of the receiver. This is the case unless the slotted insertand/or the slotted retainer are blocked from being able to be pushedback up into receiver bore or cavity, or unless the screw assemblies areotherwise uniquely configured to prevent this from happening.

SUMMARY OF THE INVENTION

The present invention differentiates from the prior art by not allowingthe receiver to be removed from the shank head once the parts aresnapped-on and connected. This is true even if the retainer can go backup into the expansion chamber. This approach or design has been found tobe more secure and to provide more resistance to pull-out forcescompared to the prior art for modular polyaxial screw designs.Collect-like structures extending downwardly from lower pressureinserts, when used in modular polyaxial screw designs, as shown in theprior art, have been found to be somewhat weak with respect to pull-outforces encountered during some spinal reduction procedures. The presentinvention is designed to solve these problems.

The present invention also differentiates from the prior art byproviding an expansion-only split or open retainer ring that isultimately positioned in sliding, pivoting relation with the shank andpositioned substantially below the shank head hemisphere in the receiverand can be a stronger, more substantial structure to resist largerpull-out forces on the assembly. Furthermore, the slitted or slottedretainer ring is also ultimately in sliding, pivoting relation with aninner surface of the receiver. The expansion only retainer has beenfound to be stronger and more secure when compared to that of the priorart which uses some type of contractile locking engagement between theparts, as described above; and, again, once assembled it cannot bedisassembled.

Thus, a polyaxial bone screw assembly according to the inventionincludes a shank having an integral upper portion illustrated as aspherical head and a body for fixation to a bone; a separate receiverdefining an upper open channel, a central bore, a lower cavity and alower opening; a compression insert; and a resilient expansion-onlysplit retainer for capturing the shank head in the receiver lowercavity, the retainer being slidingly engageable with both the shank headand a surface defining the receiver cavity. Thus, a first polyaxialarticulation is formed by the shank head and the retainer and a secondpolyaxial articulation is formed by the retainer and the receiver makinga compound articulation. In the illustrated embodiment, the shank upperportion or head is convex, more specifically, spherical, and theretainer has an inner concave surface, also illustrated as spherical, inslidable, pivoting and rotational relation thereto. The retainer alsohas an outer convex surface, illustrated as spherical, and the receiverhas an inner concave surface, illustrated as spherical, in slidable,pivoting and rotational relation thereto. Thus, cooperation between theretainer and the shank head at one side thereof and the receiver at theother side thereof allows for multiple or, again, compound articulationof the shank with respect to the receiver.

It is foreseen in some embodiments when assembled with the receiver,retainer and insert, but prior to locking, that the shank head can befrictionally engaged with, but still movable in a non-floppy manner withrespect to the insert to allow for movement of the shank to a desiredposition or angular orientation of the shank with respect to thereceiver. For example, this could be done with a tool. The insertoperatively engages the shank head and is spaced from the retainer bythe shank head. The shank can be finally locked into a fixed positionrelative to the receiver by frictional engagement between a portion ofthe insert due to a downward force placed on the compression insert by atemporary locking tool or by a closure top pressing on a rod, or otherlongitudinal connecting member, captured within the receiver bore andchannel. In the illustrated embodiments, retainers and inserts aredownloaded into the receiver, but uploaded retainer embodiments are alsoforeseen. The shank head can be positioned into the receiver lowercavity at the lower opening thereof prior to or after insertion of theshank into bone. It is also foreseen that some compression inserts mayinclude a lock and release feature for independent locking of thepolyaxial mechanism so the screw can be used like a fixed monoaxialscrew. In some embodiments the shank can be cannulated for minimallyinvasive surgery applications. The lower pressure insert and/or theretainer are both devoid of any type of receiver-retainer contractilelocking engagements with respect to the shank head, and the receiver isdevoid of any spring-tab like members.

Again, a pre-assembled receiver, compression insert and split retainermay be “pushed-on”, “snapped-on” or “popped-on” to the shank head priorto or after implantation of the shank into a vertebra. Such a “snappingon” procedure includes the steps of uploading the shank head into thereceiver lower opening, the shank head pressing against the base of thesplit retainer ring and expanding the resilient retainer out into anexpansion portion or chamber of the receiver cavity followed by anelastic return of the retainer back to an original or near nominal shapethereof after the hemisphere of the shank head or upper portion passesthrough the ring-like retainer. In such neutral or original shape, theretainer is slidable with respect to both a lower portion of the shankhead and an inner surface defining the receiver cavity, the illustratedretainer, shank and receiver surfaces being substantially spherical,with the retainer having an inner partially spherical surface and anouter partially spherical surface. However, it is foreseen that othersurface configurations or combinations may be utilized. In theillustrated embodiment, the ultimate locking of the shank between thecompression insert and the retainer is the result of a lockingexpansion-type of contact between the shank head and the split retainerand an expansion-type of non-tapered locking engagement between theretainer ring and a lower portion of the receiver cavity. The retainercan expand more in an upper portion of the receiver cavity to allow theshank head to pass through, but has restricted expansion to retain theshank head when the retainer is against the lower receiver surfacesdefining the receiver cavity. The shank head is forced down against theretainer during final locking. It is foreseen that in some embodiments,when the polyaxial mechanism is locked, the insert could be forced orwedged against surfaces of the receiver resulting in an interference,non-contractile locking engagement, allowing for adjustment or removalof the rod or other connecting member without loss of a desired angularrelationship between the shank and the receiver. This type ofindependent, non-contractile locking feature would allow the polyaxialscrew to function like a fixed monoaxial screw, which could be veryhelpful in some applications.

The compression or pressure insert (a lock and release embodiment or anon-locking embodiment) may also be configured to be independentlylocked (permanently or temporarily) by a tool or instrument, therebyallowing the pop-on polyaxial screw to be distracted, compressed and/orrotated along and around the rod to provide for improved spinalcorrection techniques. Such a tool engages the pop-on receiver from thesides and then engages the insert to force or wedge the insert down intoa locked position on the shank within the receiver. With the tool stillin place and the correction maintained, the rod is then locked withinthe receiver channel by a closure top followed by removal of the tool.This process may involve multiple screws all being manipulatedsimultaneously with multiple tools to achieve the desired correction.

Objects of the invention further include providing apparatus and methodsthat are easy to use and especially adapted for the intended use thereofand wherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a polyaxial bone screwassembly according to the present invention including a shank, areceiver, a retainer in the form of an open ring articulatable withrespect to both the shank and the receiver and a crown compressioninsert, further shown with a portion of a longitudinal connecting memberin the form of a rod and a closure top.

FIG. 2 is an enlarged top plan view of the shank of FIG. 1.

FIG. 3 is reduced cross-sectional view taken along the line 3-3 of FIG.2.

FIG. 4 is an enlarged perspective view of the receiver of FIG. 1.

FIG. 5 is a side elevational view of the receiver of FIG. 4.

FIG. 6 is a top plan view of the receiver of FIG. 4.

FIG. 7 is a bottom plan view of the receiver of FIG. 4.

FIG. 8 is an enlarged cross-sectional view taken along the line 8-8 ofFIG. 6.

FIG. 9 is an enlarged cross-sectional view taken along the line 9-9 ofFIG. 6.

FIG. 10 is an enlarged and partial perspective view of a portion of thereceiver of FIG. 4 with portions broken away to show the detail thereof.

FIG. 11 is an enlarged perspective view of the retainer of FIG. 1.

FIG. 12 is a reduced top plan view of the retainer of FIG. 11.

FIG. 13 is a bottom plan view of the retainer of FIG. 12.

FIG. 14 is a front elevational view of the retainer of FIG. 12.

FIG. 15 is a cross-sectional view taken along the line 15-15 of FIG. 12.

FIG. 16 is an enlarged perspective view of the insert of FIG. 1.

FIG. 17 is a side elevational view of the insert of FIG. 16.

FIG. 18 is a front elevational view of the insert of FIG. 16.

FIG. 19 is a bottom plan view of the insert of FIG. 16.

FIG. 20 is a top plan view of the insert of FIG. 16.

FIG. 21 is an enlarged cross-sectional view taken along the line 21-21of FIG. 20.

FIG. 22 is an enlarged cross-sectional view taken along the line 22-22of FIG. 20.

FIG. 23 is an enlarged front elevational view of the retainer andreceiver of FIG. 1 with portions of the receiver broken away to show thedetail thereof and further showing in phantom an intermediate positionof the retainer while being downloaded into the receiver.

FIG. 24 is a front elevational view with portions broken away, similarto FIG. 23, further showing the insert of FIG. 1 in enlarged sideelevation, with an early stage of assembly of the insert being shown inphantom.

FIG. 25 is a front elevational view with portions broken away, similarto FIG. 24, showing the insert rotated within the receiver during anassembly stage subsequent to that shown in FIG. 24.

FIG. 26 is an enlarged perspective view with portions broken away of theassembly shown in FIG. 25 and further showing a subsequent step ofcrimping a portion of the receiver against the insert.

FIG. 27 is a reduced side elevational view of the assembly shown in FIG.26.

FIG. 28 is a front elevational view with portions broken away, similarto FIG. 25 and shown with the crimping of FIGS. 26 and 27.

FIG. 29 is a reduced front elevational view with portions broken away,similar to FIG. 28 and further showing an alternative assembly stagewith the shank of FIG. 1 shown in partial front elevation in which theshank is first implanted in a vertebra, shown in phantom, followed byassembly with the receiver, retainer and insert.

FIG. 30 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 28 showing the shank (not implanted in avertebra) in a stage of assembly with the retainer, the retainer beingpushed up into engagement with the insert.

FIG. 31 is an enlarged partial front elevational view with portionsbroken away, similar to FIG. 30, and having further portions broken awayshowing the retainer in an expanded state about an upper portion of theshank.

FIG. 32 is a partial front elevational view with portions broken away,similar to FIG. 31, and showing a subsequent step of the retainer beingreturned to a neutral state capturing the shank within the receiver.

FIG. 33 is a partial front elevational view with portions broken away,similar to FIG. 32, the shank upper portion and retainer being pulleddownwardly into the receiver.

FIG. 34 is a partial front elevational view with portions broken away,similar to FIG. 33 showing a subsequent step of lowering the insert intoengagement with the shank.

FIG. 35 is a partial front elevational view of the assembly as shown inFIG. 34 with further portions broken away to show the detail thereof.

FIG. 36 is a partial front elevational view of the assembly of FIG. 35,further showing the shank being articulated at an angle with respect tothe receiver.

FIG. 37 is a partial front elevational view of the assembly of FIG. 35,further showing the shank and the retainer being articulated at an anglewith respect to the receiver.

FIG. 38 is a reduced perspective view of the assembly of FIG. 35 furthershown in engagement with the rod and closure of FIG. 1 and with portionsbroken away to show the detail thereof.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

With reference to FIGS. 1-38 the reference number 1 generally representsa polyaxial bone screw apparatus or assembly according to the presentinvention. The assembly 1 includes a shank 4, that further includes abody 6 integral with an upwardly extending upper portion or head-likecapture structure 8; a receiver 10; a retainer structure illustrated asa resilient open, articulatable ring 12, and a compression or pressureinsert 14. The receiver 10, retainer 12 and compression insert 14 areinitially assembled and may be further assembled with the shank 4 eitherprior or subsequent to implantation of the shank body 6 into a vertebra17, as will be described in greater detail below. FIGS. 1 and 38 furthershow a closure structure 18 for capturing a longitudinal connectingmember, for example, a rod 21 which in turn engages the compressioninsert 14 that presses against the shank upper portion 8 into fixedfrictional contact with the retainer 12, so as to capture, and fix thelongitudinal connecting member 21 within the receiver 10 and thus fixthe member 21 relative to the vertebra 17. The receiver 10 and the shank4 cooperate in such a manner that the receiver 10 and the shank 4 can besecured at any of a plurality of angles, articulations or rotationalalignments relative to one another and within a selected range of anglesboth from side to side and from front to rear, to enable flexible orarticulated engagement of the receiver 10 with the shank 4 until bothare locked or fixed relative to each other near the end of animplantation procedure. The illustrated rod 21 is hard, stiff,non-elastic and cylindrical, having an outer cylindrical surface 22. Itis foreseen that in other embodiments, the rod 21 may be elastic,deformable and/or of a different cross-sectional geometry. In suchcases, the closure top could deform the rod and press directly on theinsert 14.

The shank 4, best illustrated in FIGS. 1-3, is elongate, with the shankbody 6 having a helically wound bone implantable thread 24 (single ordual lead thread form) extending from near a neck 26 located adjacent tothe upper portion or head 8, to a tip 28 of the body 6 and extendingradially outwardly therefrom. During use, the body 6 utilizing thethread 24 for gripping and advancement is implanted into the vertebra 17(e.g., see FIG. 29) leading with the tip 28 and driven down into thevertebra with an installation or driving tool (not shown), so as to beimplanted in the vertebra to a location at or near the neck 26, as morefully described in the paragraphs below. The shank 4 has an elongateaxis of rotation generally identified by the reference letter A.

The neck 26 extends axially upward from the shank body 6. The neck 26may be of the same or is typically of a slightly reduced radius ascompared to an adjacent upper end or top 32 of the body 6 where thethread 24 terminates. Further extending axially and outwardly from theneck 26 is the shank upper portion or head 8 that provides a connectiveor capture apparatus disposed at a distance from the upper end 32 andthus at a distance from the vertebra 17 when the body 6 is implanted insuch vertebra.

The shank upper portion 8 is configured for a pivotable connectionbetween the shank 4 and the retainer 12 and receiver 10 prior to fixingof the shank 4 in a desired position with respect to the receiver 10.The shank upper portion 8 has an outer, convex and substantiallyspherical surface 34 that extends outwardly and upwardly from the neck26 and terminates at a substantially planar top or rim surface 38. Thespherical surface 34 has an outer radius configured for frictional,sliding cooperation with a concave surface of the compression insert 14,as well as ultimate frictional engagement with the insert as will bediscussed more fully in the paragraphs below. The top surface 38 issubstantially perpendicular to the axis A. The spherical surface 34shown in the present embodiment is substantially smooth, but in someembodiments may include a roughening or other surface treatment and issized and shaped for cooperation and ultimate frictional engagement withthe compression insert 14 as well as ultimate frictional engagement withthe retainer 12. The shank spherical surface 34 is locked into placeexclusively by the insert 14 and the retainer 12 and not by innersurfaces defining the receiver cavity, the shank being held in spacedrelation with the receiver by the retainer 12.

A counter sunk substantially planar base 45 partially defines aninternal drive feature or imprint 46. The illustrated internal drivefeature 46 is an aperture formed in the top surface 38 and has a starshape designed to receive a driving tool (not shown) of an Allen wrenchtype, into the aperture for rotating and driving the bone screw shank 4.It is foreseen that such an internal tool engagement structure may takea variety of tool-engaging forms and may include one or more aperturesof various shapes, such as a hex shape, a pair of spaced apart aperturesor a multi-lobular or star-shaped aperture, such as those sold under thetrademark TORX, or the like. The seat or base surface 45 of the drivefeature 46 is disposed substantially perpendicular to the axis A withthe drive feature 46 otherwise being coaxial with the axis A. The driveseat 45 may include beveled or stepped surfaces that may further enhancegripping with the driving tool. In operation, a driving tool (not shown)is received in the internal drive feature 46, being seated at the base45 and engaging the plurality of faces of the drive feature 46 for bothdriving and rotating the shank body 6 into the vertebra 17, eitherbefore the shank 4 is attached to the receiver 10 or after the shank 4is attached to the receiver 10, with the shank body 6 being driven intothe vertebra 17 with the driving tool extending into the receiver 10.

The shank 4 shown in the drawings is cannulated, having a small centralbore 50 extending an entire length of the shank 4 along the axis A. Thebore 50 is defined by an inner cylindrical wall of the shank 4 and has acircular opening at the shank tip 28 and an upper opening communicatingwith the external drive 46 at the driving seat 45. The bore 50 iscoaxial with the threaded body 6 and the upper portion 8. The bore 50provides a passage through the shank 4 interior for a length of wire(not shown) inserted into the vertebra 17 prior to the insertion of theshank body 6, the wire providing a guide for insertion of the shank body6 into the vertebra 17.

To provide a biologically active interface with the bone, the threadedshank body 6 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With particular reference to FIGS. 1 and 4-10, the receiver 10 has agenerally U-shaped appearance with partially discontinuous and partiallyplanar and cylindrical inner and outer profiles. The receiver 10 has anaxis of rotation B that is shown in FIG. 1 as being aligned with and thesame as the axis of rotation A of the shank 4, such orientation beingdesirable, but not required during assembly of the receiver 10 with theshank 4 (see, e.g., FIG. 29 showing the receiver 10 being “popped on” toa shank 4 that is implanted in a vertebra 17 and disposed at an anglewith respect to the receiver). After the receiver 10 is pivotallyattached to the shank 4, either before or after the shank 4 is implantedin a vertebra 17, the axis B is typically disposed at an angle withrespect to the axis A, as shown, for example, in FIGS. 36 and 37.

The receiver 10 includes a partially curved or cylindrical and partiallyplanar and diverging base 60 defining a bore or inner cavity, generally61, the base 60 being integral with a pair of opposed upstanding arms 62forming a cradle and defining a channel 64 between the arms 62 with anupper opening, generally 66, and a U-shaped lower channel portion orseat 68, the channel 64 having a width for operably snugly receiving therod 21 or portion of another longitudinal connector between the arms 62;the channel 64 communicating with the base cavity 61. Outer front andrear opposed substantially planar arm surfaces 69 define an outerperimeter of the channel 64 at the arms 62 and about the channel seat68.

Each of the arms 62 has an interior surface, generally 70, that includesvarious inner cylindrical profiles, an upper one of which is a partialhelically wound guide and advancement structure 72 located adjacent topsurfaces 73 of each of the arms 62. In the illustrated embodiment, theguide and advancement structure 72 is a partial helically woundinterlocking flangeform configured to mate under rotation with a similarstructure on the closure structure 18, as described more fully below.However, it is foreseen that for certain embodiments of the invention,the guide and advancement structure 72 could alternatively be asquare-shaped thread, a buttress thread, a reverse angle thread or otherthread-like or non-thread-like helically wound discontinuous advancementstructures, for operably guiding under rotation and advancing theclosure structure 18 downward between the arms 62, as well as eventualtorquing when the closure structure 18 abuts against the rod 21 or otherlongitudinal connecting member. It is foreseen that the arms could havebreak-off extensions.

An opposed pair of rounded off triangular or delta-shaped tool receivingand engaging apertures, generally 74, each having a through bore formedby an upper arched surface 75 and a substantially planar bottom surface75′, are formed on outer surfaces 76 of the arms 62. Each through boresurface 75 and 75′ extends through the arm inner surface 70. Theapertures 74 with through bore portions 75 and 75′ are sized and shapedfor receiving locking, unlocking and other manipulation tools and mayaid in receiving and downloading the retainer ring 12 during top loadingof the retainer 12 into the receiver 10. Each aperture 74 furtherincludes a sloping tool alignment surface 77 that generally surroundsthe arched bore portion 75 and does not extend completely through therespective arm 62, the sloping surfaces 77 terminating at asubstantially planar thin wall 78, the wall 78 defining the bore portion75 and disposed at an angle to the wall 78. Each wall 78 furtherincludes a further recessed crimping portion or area 79 that is alsopartially formed in one of the sloping surfaces 77. As will be describedin greater detail below, during an assembly stage, each of the fourcrimping portions 79 is pressed or crimped into the insert 14 to aid inretaining the insert 14 in alignment with the receiver and prohibitrotation of the retainer with respect to the receiver, but to allow formovement of the retainer up and down along the receiver axis B. In apreferred embodiment, such up and down movement is possible only throughthe application of some upward or downward force, allowing for theinsert to be placed in an out-of-the-way location during insertion ofthe shank head 8 through the retainer 12 and then later, for anon-floppy frictional engagement between the insert 14 and the shankupper portion 8 during intermediate assembly and/or implantation stepsand positions prior to locking the shank into place between the insert14 and the retainer 12. In other embodiments of the invention, otherwalls or surfaces defining the aperture 74 or other material definingother apertures or grooves may be inwardly crimped. It is noted that theillustrated receiver 10 is an integral structure and devoid of anyspring tabs or collet-like structures. Alternatively, in someembodiments, spring tabs or other movable structure may be included onthe receiver 10 or the insert 14 for retaining the insert 14 in adesired position, with regard to rotation and axial movement (along theaxis A) with respect to the receiver 10. Preferably the insert and/orreceiver are configured with structure for blocking rotation of theinsert with respect to the receiver, but allowing some up and downmovement of the insert with respect to the receiver during the assemblyand implant procedure.

Formed in each surface 77 and also partially in each arm surface 76 andlocated opposite the planar surface 75′ is another tool receiving recess80 having a somewhat rectangular profile. A further recess 81 is locateddirectly above the recess 80, the recess 81 being formed in each armsurface 76 and located between the aperture 74 and the arm top surface73. Each recess 81 has a substantially rectangular profile with a basesurface 82 that does not extend all the way through the respective arm61 and further includes an upper curved portion 83 having ahalf-circular profile. Four V-shaped grooves 84 are formed in each ofthe arm surfaces 76 at each of the front and rear planar surfaces 69,each groove 84 running from the respective top surface 73 to a locationmidway along the receiver arm on either side of the aperture 74. Some orall of the apertures or grooves 74, 81 and 84 may be used for holdingthe receiver 10 during assembly with the insert 14, the retainer 12 andthe shank 4; during the implantation of the shank body 6 into a vertebrawhen the shank is pre-assembled with the receiver 10; during assembly ofthe bone anchor assembly 1 with the rod 21 and the closure structure 18;and during lock and release adjustment of the some inserts of theinvention with respect to the receiver 10, either into or out offrictional engagement with the inner surfaces of the receiver 10 as willbe described in greater detail below. It is foreseen that tool receivinggrooves, depressions or apertures may be configured in a variety ofshapes and sizes and be disposed at other locations on the receiver arms62.

Returning to the interior surface 70 of the receiver arms 62, locatedbelow the guide and advancement structure 72 is a discontinuouscylindrical surface 88 partially defining a run-out feature for theguide and advancement structure 72. The cylindrical surface 88 has adiameter equal to or slightly greater than a greater diameter of theguide and advancement structure 72. Moving downwardly in a directiontoward the base 60, adjacent the cylindrical surface 88 of each arm is arun-out seat or surface 89 that extends inwardly toward the axis B andslopes toward the axis B. Adjacent to and located below the surface 84is another cylindrical surface 90 having a diameter smaller than thediameter of the surface 82. The through bore surfaces 75 and 75′ extendthrough the arms primarily at the surfaces 90, with an upper portion ofeach arch 75 extending through one of the surfaces 88. Located near eachaperture surface 75 is an inner surface portion 92 of the crimp areas orportions 79, the surface portions 92 engaging the insert 14 when thethin wall at the surface portion 79 is crimped toward the insert 14during assembly of such insert in the receiver 10 as will be describedin greater detail below. The inner discontinuous surface 90 found on thereceiver arms 62 also extends downwardly into the receiver cavity 61 andthus defines an upper expansion area for the retainer 12. The surface 90is disposed parallel to the receiver axis B and is sized to receiveportions of the insert 14, and in some embodiments may be sized toprovide a locking interference fit with a cylindrical portion of alocking insert.

Further, with respect to the base 60 and more specifically, the basecavity 61, a lower portion of the surface 90 that extends into the baseand partially defines the base cavity 61 terminates at a stepped orsloping surface or surfaces 95 inwardly directed toward the axis B andsized and shaped to receive the retainer 12. The surface 90 defines acircumferential recess that is sized and shaped to receive the retainer12 as it expands around the shank upper portion 8 as the shank 8 movesupwardly toward the channel 64 during assembly. The insert 14 providesan upper stop or restriction to prevent the expanded retainer 12 frommoving upwardly with the shank portion 8, the insert 14 preventing theretainer 12 from passing upwardly out of the cavity 61 whether theretainer 12 is in a partially or fully expanded position or state.Adjacent and below the stepped or sloping surfaces 95 is an innerspherical surface 100 sized and shaped for sliding relation and ultimatefrictional contact with an outer surface of the retainer 12 as will bedescribed in greater detail below. The stepped surfaces 95 allow forsliding gradual movement of the retainer 12 into the space defined bythe surface 100 and ultimate seating of the retainer 12 against thesurface 100 and above and along a terminal edge 102 of the surface 100.Located below and adjacent to the edge 102 is a beveled or flared bottomopening surface 107, the surface 107 communicating with an exterior basesurface 108 of the base 60, defining a lower opening, generally 110,into the base cavity 61 of the receiver 10.

With particular reference to FIGS. 1 and 11-15, the lower open or splitretainer 12, that operates to capture the shank upper portion 8 withinthe receiver 10, has a central axis C that may be operationally the sameor different than the axis B associated with the receiver 10 or the axisA associated with the shank 4 when the shank upper portion 8 and theretainer 12 are installed within the receiver 10. The retainer ring isthus articulatable and slidable with respect to both the shank 4 and thereceiver 10 until locked into place. The retainer ring 12 is made from aresilient material, such as a stainless steel or titanium alloy, so thatthe retainer 12 may be expanded during various steps of assembly as willbe described in greater detail below. The retainer 12 has a centralchannel or hollow through bore, generally 121, that passes entirelythrough the ring 12 from a top surface 122 to a bottom surface 124thereof. The bore 121 is defined by an inner discontinuous sphericalsurface 125 that runs from adjacent the top surface 122 to adjacent thebottom surface 124. The retainer 12 further includes an outer sphericalsurface 130 that runs from adjacent the top surface 122 to adjacent thebottom surface 124. The inner spherical surface 125 is sized and shapedfor closely slidingly receiving the shank head 8 at the surface 34 andultimate frictional locking there-against and the outer sphericalsurface 130 is sized and shaped for close sliding engagement with theinner spherical surface 100 of the receiver 10 and ultimate frictionallocking there-against. In some embodiments of the invention, spacednotches (not shown) may be formed in the spherical surface 130 toreceive a holding and manipulation tool (not shown). In some embodimentsfurther notches on inner or outer surfaces of the retainer may be madeto evenly distribute stress across the entire retainer 12 duringexpansion thereof.

The resilient retainer 12 further includes first and second endsurfaces, 134 and 135 disposed in spaced relation to one another whenthe retainer is in a neutral non-compressed state. The surface 134 and135 may also be touching when the retainer is in a neutral state. Bothend surfaces 134 and 135 run from the top surface 122 to the bottomsurface 124 and are illustrated as running at an oblique angle to suchtop and bottom surfaces. In other embodiments of the invention, thesurfaces 134 and 135 may be disposed substantially perpendicular to thetop surface 122 and the bottom surface 124. A width X between thesurfaces 134 and 135 is very narrow (slit may be made by EDM process) toprovide stability to the retainer 12 during operation. Because theretainer 12 is top loadable in a neutral state and the retainer 12 doesnot need to be compressed to fit within the receiver cavity 61, thewidth X may be much smaller than might be required for a bottom loadedcompressible retainer ring. The gap X functions only in expansion toallow the retainer 12 to expand about the shank upper portion 8. Thisresults in a stronger retainer that provides more surface contact withthe shank upper portion 8 upon locking, resulting in a sturdierconnection with less likelihood of failure than a retainer ring having agreater gap. Furthermore, because the retainer 12 is only expanded andnever compressed inwardly, the retainer 12 does not undergo themechanical stress that typically is placed on spring ring type retainersknown in the prior art that are both compressed inwardly and expandedoutwardly during assembly. It is foreseen that in some embodiments ofthe invention, the retainer 12 inner surfaces may include a rougheningor additional material to increase the friction fit against the shankupper portion 8 prior to lock down by the rod 21 or other longitudinalconnecting member.

With particular reference to FIGS. 1 and 16-22, the crown compressioninsert 14 is illustrated that is sized and shaped to be received by anddown-loaded into the receiver 10 at the upper opening 66. Thecompression insert 14 has an operational central axis that is the sameas the central axis B of the receiver 10. In operation, the insertadvantageously frictionally engages the bone screw shank upper portion8, allowing for un-locked but non-floppy placement of the angle of theshank 4 with respect to the receiver 10 during surgery prior to lockingof the shank with respect to the receiver near the end of the procedure.In some embodiments of the invention, the insert that has locked theshank 4 in a desired angular position with respect to the receiver 10,by, for example, compression from the rod 21 and closure top 18, mayalso be forced into an interference fit engagement with the receiver 10at the inner cylindrical surface 90, for example, and thus be capable ofretaining the shank 6 in a locked position even if the rod 21 andclosure top 18 are removed. Such locked position may also be released bythe surgeon if desired by features included in the insert 14, such asridges, grooves and/or apertures, bores or holes. The non-locking insert14 (as well as an alternative locking insert) is preferably made from asolid resilient material, such as a stainless steel or titanium alloy,so that portions of the insert may be snapped or popped onto the shankupper portion 8 as well as pinched or pressed against and un-wedged (incertain embodiments) from the receiver 10 with a release tool.

The non-locking crown collet compression insert 14 includes asubstantially cylindrical body 136 integral with a pair of upstandingarms 137. A bore, generally 140, is disposed primarily within andthrough the body 136 and communicates with a generally U-shaped throughchannel formed by a saddle 141 that is partially defined by theupstanding arms 137 and partially by the body 136. The saddle 141 issized and shaped to closely, snugly engage the cylindrical rod 21 andincludes a curved lower seat 142. It is foreseen that an alternativeembodiment may be configured to include planar holding surfaces thatclosely hold a square or rectangular bar as well as hold a cylindricalrod-shaped, cord, or sleeved cord longitudinal connecting member. Thearms 137 disposed on either side of the saddle 141 extend upwardly fromthe body 136. The arms 137 are sized and configured for ultimateplacement at or near the cylindrical run-out surface 88 and innersurface 90 located below the receiver guide and advancement structure72. It is foreseen that in some embodiments of the invention, the insertarms 137 may be extended and the closure top configured such the armsultimately directly engage the closure top 18 for locking of thepolyaxial mechanism, for example, when the rod 21 is made from adeformable material. In such embodiments, the insert 14 would include arotation blocking structure or feature on an outer surface thereof thatabuts against cooperating structure located on an inner wall of thereceiver 10, preventing rotation of the insert with respect to thereceiver when the closure top is rotated into engagement with theinsert, especially when there is no rod in place. In the presentembodiment, each of the arms 137 includes an outer surface 143 that isillustrated as partially cylindrical and runs from the substantiallyplanar top surfaces 144 to an inwardly sloping lower surface 150 of theinsert 14, the surface 150 extending about the body 136 and the arms 137and terminating at an annular rim or edge 151. The surface 150 isadvantageously sloped or angled to provide clearance between the insert14 and the retainer 12 when the retainer and shank 4 are articulated orpivoted with respect to one another and with respect to the receiver 10.Also, the sloping surface 150 that runs from the lower edge or rim 151outwardly and upwardly away from the axis B and toward the uppersurfaces 144 provides a sliding outwardly and upwardly directed surfacefor guiding the top surface 122 of the retainer 12 during expansion ofthe retainer inner spherical surface 125 about the shank head 8spherical surface 34 as will be discussed in greater detail below.

The surfaces 143 are sized and shaped to generally fit within thereceiver arms 62. The arm outer surfaces 143 further include notches orgrooves formed thereon for receiving manipulation, unlocking and lockingtools. Although not shown, each surface 143 may include one or morethrough bores or other apertures for receiving tooling, particularlyuseful for alternative locking embodiments (not shown). Centrallylocated (in some embodiments below a through bore) and formed in eachsurface 143 is a delta or triangular notch or recess, generally 156, forreceiving tooling defined in part by an upper sloping surface 157 andintersecting a lower planar surface 158 disposed substantiallyperpendicular to a central axis of the insert 14 (and the axis B of thereceiver when the insert is disposed within the receiver). Each of thesurfaces 167 and surface 168 cooperate and align with the respectivereceiver aperture through bore surfaces 77 and 75′ when the insert 14 iscaptured and operationally positioned within the receiver 10 as will bedescribed in greater detail below. In the illustrated embodiments, alsoformed in each surface 143 are a pair of spaced v- or squared-offnotches or grooves 160 and 161 that run from the respective top surface144 to near the sloping surface 157 of the central delta cut or notch156. The grooves 160 and 161 cooperate with the receiver crimp wall 79inner surfaces 92 to aid in alignment of the insert channel saddle 141with the receiver channel 64 as shown, for example in FIGS. 25-27. Theillustrated pair of grooves 160 and 161 are disposed substantiallyparallel to the central axis of the insert 14, running from one of thetop surfaces 144 to respective lower or bottom surfaces 162 and 163.

The u-shaped channel formed by the saddle 141 is also partially definedby opposed inner planar surfaces 165 located near the arm top surfaces144. The saddle 141 also communicates with the bore 140 at an innercylindrical surface 166, the surface 166 located centrally within theinsert body 136 and further communicating with a lower concave surfaceportion 168 having a generally spherical profile with a radius the sameor substantially similar to a radius of the surface 34 of the shankupper portion or head 8. The surface 168 terminates at the edge or rim151. It is foreseen that in some embodiments of the invention a portionor all of the surface 168 may include ridges, stepped surfaces or asurface roughening or texture, such as scoring or knurling, or the like,for enhancing frictional engagement with the shank upper portion 8.

The insert bore 140 is sized and shaped to receive the driving tool (notshown) therethrough that engages the shank drive feature 46 when theshank body 6 is driven into bone with the receiver 10 attached. Also, inalternative locking embodiments, the bore 140 may receive a manipulationtool used for releasing the such insert from a locked position with thereceiver, the tool pressing down on the shank and also gripping theinsert at the opposed through bores or with other tool engagingfeatures. A manipulation tool for un-wedging a locking insert from thereceiver 10 may also access the such tooling bores from the receiverthrough bores 74. The illustrated insert 14 may further include otherfeatures, including grooves and recesses for manipulating and holdingthe insert 14 within the receiver 10 and providing adequate clearancebetween the retainer 12 and the insert 14.

The insert body 136 located between the arms 137 has an outer diameterslightly smaller than a diameter between crests of the guide andadvancement structure 72 of the receiver 10, allowing for top loading ofthe compression insert 14 into the receiver opening 66, with the arms137 of the insert 14 being located between the receiver arms 62 duringinsertion of the insert 14 into the receiver 10. Once the arms 137 ofthe insert 14 are generally located beneath the guide and advancementstructure 72, the insert 14 is rotated into place about the receiveraxis B until the top surfaces 144 are located directly below the guideand advancement structure 72 as will be described in greater detailbelow.

With reference to FIGS. 1 and 38, the illustrated elongate rod orlongitudinal connecting member 21 (of which only a portion has beenshown) can be any of a variety of implants utilized in reconstructivespinal surgery, but is typically a cylindrical, elongate structurehaving the outer substantially smooth, cylindrical surface 22 of uniformdiameter. The rod 21 may be made from a variety of metals, includinghard and soft metal alloys and hard and soft or deformable and lesscompressible plastics, including, but not limited to rods made ofelastomeric, polyetheretherketone (PEEK) and other types of materials.

Longitudinal connecting members for use with the assembly 1 may take avariety of shapes, including but not limited to rods or bars of oval,rectangular or other curved or polygonal cross-section. The shape of theinsert 14 may be modified so as to closely hold, and if desired, fix orslidingly capture the longitudinal connecting member to the assembly 1.Some embodiments of the assembly 1 may also be used with a tensionedcord. Such a cord may be made from a variety of materials, includingpolyester or other plastic fibers, strands or threads, such aspolyethylene-terephthalate. Furthermore, the longitudinal connector maybe a component of a longer overall dynamic stabilization connectingmember, with cylindrical or bar-shaped portions sized and shaped forbeing received by the compression insert 14 of the receiver having aU-shaped, rectangular- or other-shaped channel, for closely receivingthe longitudinal connecting member. The longitudinal connecting membermay be integral or otherwise fixed to a bendable or damping componentthat is sized and shaped to be located between adjacent pairs of bonescrew assemblies 1, for example. A damping component or bumper may beattached to the longitudinal connecting member at one or both sides ofthe bone screw assembly 1. A rod or bar (or rod or bar component) of alongitudinal connecting member may be made of a variety of materialsranging from soft deformable plastics to hard metals, depending upon thedesired application. Thus, bars and rods of the invention may be made ofmaterials including, but not limited to metal and metal alloys includingbut not limited to stainless steel, titanium, titanium alloys and cobaltchrome; or other suitable materials, including plastic polymers such aspolyetheretherketone (PEEK), ultra-high-molecular weight-polyethylene(UHMWP), polyurethanes and composites, including composites containingcarbon fiber, natural or synthetic elastomers such as polyisoprene(natural rubber), and synthetic polymers, copolymers, and thermoplasticelastomers, for example, polyurethane elastomers such aspolycarbonate-urethane elastomers.

With reference to FIGS. 1 and 38, the closure structure or closure top18 shown with the assembly 1 is rotatably received between the spacedarms 62 of the receiver 10. It is noted that the closure 18 top could bea twist-in or slide-in closure structure. The illustrated closurestructure 18 is substantially cylindrical and includes a an outerhelically wound guide and advancement structure 182 in the form of aflange that operably joins with the guide and advancement structure 72disposed on the arms 62 of the receiver 10. The flange form utilized inaccordance with the present invention may take a variety of forms,including those described in Applicant's U.S. Pat. No. 6,726,689, whichis incorporated herein by reference. Although it is foreseen that theclosure structure guide and advancement structure could alternatively bea buttress thread, a square thread, a reverse angle thread or otherthread like or non-thread like helically wound advancement structure,for operably guiding under rotation and advancing the closure structure18 downward between the arms 62 and having such a nature as to resistsplaying of the arms 62 when the closure structure 18 is advanced intothe channel 64, the flange form illustrated herein as described morefully in Applicant's U.S. Pat. No. 6,726,689 is preferred as the addedstrength provided by such flange form beneficially cooperates with andcounters any reduction in strength caused by the inset surfaces 69resulting in a reduced profile of the illustrated receiver 10 at theU-shape channel, such surfaces advantageously engaging longitudinalconnecting member components as will be further described below. Theillustrated closure structure 18 also includes a top surface 184 with aninternal drive 186 in the form of an aperture that is illustrated as astar-shaped internal drive such as that sold under the trademark TORX,or may be, for example, a hex drive, or other internal drives such asslotted, tri-wing, spanner, two or more apertures of various shapes, andthe like. A driving tool (not shown) sized and shaped for engagementwith the internal drive 166 is used for both rotatable engagement and,if needed, disengagement of the closure 18 from the receiver arms 62. Itis also foreseen that the closure structure 18 may alternatively includea break-off head designed to allow such a head to break from a base ofthe closure at a preselected torque, for example, 70 to 140 inch pounds.Such a closure structure would also include a base having an internaldrive to be used for closure removal. A base or bottom surface 188 ofthe closure is planar and further includes a rim 190 and may or may notinclude a further include a central point (not shown), the rim 190 andor the point (not shown) for engagement and penetration into the surface22 of the rod 21 in certain embodiments of the invention. The closuretop 18 may further include a cannulation through bore (not shown)extending along a central axis thereof and through the top and bottomsurfaces thereof. Such a through bore provides a passage through theclosure 18 interior for a length of wire (not shown) inserted therein toprovide a guide for insertion of the closure top into the receiver arms62.

Preferably the receiver 10, the retainer 12 and the compression insert14 are assembled at a factory setting that includes tooling for holding,pressing and alignment of the component pieces as well as compressing orexpanding the insert 14 arms, if needed, as well as crimping a portionof the receiver 10 toward the insert 14. In some circumstances, theshank 4 is also assembled with the receiver 10, the retainer 12 and thecompression insert 14 at the factory. In other instances, it isdesirable to first implant the shank 4, followed by addition of thepre-assembled receiver, retainer and compression insert at the insertionpoint. In this way, the surgeon may advantageously and more easilyimplant and manipulate the shanks 4, distract or compress the vertebraewith the shanks and work around the shank upper portions or headswithout the cooperating receivers being in the way. In other instances,it is desirable for the surgical staff to pre-assemble a shank of adesired size and/or variety (e.g., surface treatment of roughening theupper portion 8 and/or hydroxyapatite on the shank 6), with thereceiver, retainer and compression insert. Allowing the surgeon tochoose the appropriately sized or treated shank 4 advantageously reducesinventory requirements, thus reducing overall cost.

Pre-assembly of the receiver 10, retainer 12 and compression insert 14is shown in FIGS. 23-28. First, the retainer 12 is downloaded in asideways manner into the receiver 10 through the upper opening 66 withthe outer surface 130 facing the receiver channel seat 68. The retainer12 is then lowered between the arms 62 and toward the receiver base 60as shown in phantom in FIG. 23, the retainer being turned or tilted to aposition within the receiver base 60 inner cavity 61 wherein theretainer bottom surface 124 is manipulated to a position facing thespherical surface 100 and then the surface 130 is seated upon the innerspherical surface 100 as shown in solid lines in FIG. 23. With referenceto FIG. 24, the compression insert 14 is then downloaded into thereceiver 10 through the upper opening 66 with the bottom rim 151 facingthe receiver arm top surfaces 73 and the insert arms 137 located betweenthe opposed receiver arms 62. The insert 14 is then lowered toward thechannel seat 68 until the insert 14 arm upper surfaces 144 are adjacentthe run-out area defined by the surfaces 88 of the receiver 10 locatedbelow the guide and advancement structure 72. Thereafter, the insert 14is rotated in a clockwise or counter-clockwise manner about the receiveraxis B until the upper arm surfaces 144 are directly below the guide andadvancement structure 72 as illustrated in FIG. 25 with the U-shapedchannel 141 of the insert 14 aligned with the U-shaped channel 64 of thereceiver 10. In some embodiments, the insert arms 137 may need to becompressed slightly during rotation to clear inner surfaces of thereceiver arms 62. As shown in FIGS. 25-27, the outer cylindricalsurfaces 143 of the insert 14 are received within the cylindricalsurfaces 88 and 90 of the receiver. With particular reference to FIGS.26 and 27, the receiver thin walls of the crimping area 79 are thenpressed inwardly toward the axis B by inserting a tool (not shown) intothe receiver apertures 74, the tool pressing the sloped surface walls 77until the receiver inner wall surfaces 92 engage the insert 14 at eachof the grooves 160 and 161 formed into the outer cylindrical surface 143of each of the insert arms 137. The crimping of the opposed wallsurfaces 87 into the groves 160 and 161 keeps the insert 14 U-shapedchannel 141 substantially aligned with the receiver U-shaped channel 64,but allows for upward and downward movement of the insert 14 along thereceiver axis B during bottom loading of the shank 4 as shown in FIG.29, for example. However, such upward and downward movement requiressome force, as the four-point frictional engagement between the insertand the receiver advantageously keeps the insert at a desired axiallocation and is not a floppy or loose sliding engagement. Thus, thecrimping of the receiver walls 77 prohibits rotation of the insert 14about the receiver axis B but allows for limited axial movement of theinsert 14 with respect to the receiver 10 along the axis B when someforce is exerted to slide the crimped surfaces 87 up or down along thegrooves 160 and 161. As illustrated in FIG. 28, the insert 14 arms 137are fully captured within the receiver 10 by the guide and advancementstructure 72 prohibiting movement of the insert 14 up and out throughthe receiver opening 66 as well as by the retainer 12 and the receiverannular surface 104 located in the receiver 10 base 60 below the insert14. Also as illustrated in FIG. 28, the insert 14 may be desirably movedupwardly in the receiver 10 until an insert top surface 144 abutsagainst the guide and advancement structure 72. FIG. 28 illustrates apreferred arrangement for shipping of the receiver, retainer and insertcombination as well as a preferred upward and out-of-the-way positionfor the insert 14 during assembly with the shank 4. In some embodimentsof the invention, top or side surfaces of the insert 14 may include aresilient projection or projections for temporarily frictionallyengaging with an inner surface of the receiver 10 to hold the insert 14in an upper portion of the receiver 10 during some of the assemblysteps, also providing a frictional but slidable fit between the insert14 and the receiver 10.

At this time, the receiver, insert and retainer combination are readyfor shipping to an end user, with both the compression insert 14 and theretainer 12 captured within the receiver 10 in a manner thatsubstantially prevents movement or loss of such parts out of thereceiver 10. The receiver 10, compression insert 14 and the retainer 12combination may now be assembled with the shank 4 either at the factory,by surgery staff prior to implantation, or directly upon an implantedshank 4 as shown, for example, in FIG. 29, with the shank axis A and thereceiver axis B either being aligned during assembly as shown in FIG. 30and most of the drawings figures illustrating the assembly process, orthe axes being at an angle with respect to one another as shown in FIG.29.

As illustrated in FIG. 29, the bone screw shank 4 or an entire assembly1 made up of the assembled shank 4, receiver 10, retainer 12 andcompression insert 14, is screwed into a bone, such as the vertebra 17,by rotation of the shank 4 using a suitable driving tool (not shown)that operably drives and rotates the shank body 6 by engagement thereofat the internal drive 46. Specifically, the vertebra 17 may bepre-drilled to minimize stressing the bone and have a guide wire (notshown) inserted therein to provide a guide for the placement and angleof the shank 4 with respect to the vertebra. A further tap hole may bemade using a tap with the guide wire as a guide. Then, the bone screwshank 4 or the entire assembly 1 is threaded onto the guide wireutilizing the cannulation bore 50 by first threading the wire into theopening at the bottom 28 and then out of the top opening at the drivefeature 46. The shank 4 is then driven into the vertebra using the wireas a placement guide. It is foreseen that the shank and other bone screwassembly parts, the rod 21 (also having a central lumen in someembodiments) and the closure top 18 (also with a central bore) can beinserted in a percutaneous or minimally invasive surgical manner,utilizing guide wires. When the shank 4 is driven into the vertebra 17without the remainder of the assembly 1, the shank 4 may either bedriven to a desired final location or may be driven to a locationslightly above or proud to provide for ease in assembly with thepre-assembled receiver, compression insert and retainer.

With reference to FIGS. 29, 30 and 31, the pre-assembled receiver,insert and retainer are placed above the shank upper portion 8 until theshank upper portion is received within the opening 110. As the shankupper portion 8 is moved into the interior 61 of the receiver basedefined by the spherical surface 100, the shank upper portion 8 pressesthe retainer 12 upwardly into the portion of the receiver cavity 61defined by the cylindrical surface 90. With particular reference toFIGS. 30 and 31, as the portion 8 continues to move upwardly toward thechannel 64, the top surface 122 of the retainer 12 abuts against thelower or bottom frusto-conical or otherwise outwardly sloping surface150 of the insert 14, limiting and directing upward movement of theretainer 12 and forcing outward movement of the retainer 12 towards thecylindrical surface 90 that defines an expansion area or chamber for theretainer 12 as the shank 4 continues to move upwardly with respect tothe retainer 12. As is shown in FIGS. 30-32, the insert 14 is prohibitedfrom moving upwardly in the receiver by contact between the insert armtop surface 144 with the receiver guide and advancement structure 72.With further reference to FIG. 31 and also with reference to FIGS. 32and 33, the retainer 12 begins to contract about the spherical surface34 as the center of the sphere of the head 8 passes beyond the center ofthe retainer expansion recess defined by the surface 125. At this timealso, the spherical surface 34 moves into engagement with the insert 14spherical surface 168.

With reference to FIG. 33, the shank 4 and retainer 12 may then bemanipulated further downwardly into a desired seated position on thereceiver inner spherical surface 100 by either an upward pull on thereceiver 10 or, in some cases, by driving the shank 4 further into thevertebra 17. Then, with reference to FIG. 34, the insert 14 may bepressed downwardly with a tool (not shown) onto the shank head 8spherical surface 34. At this time, the insert 14 surface 168 and thesurface 34 are in a fairly tight friction fit, the surface 34 beingpivotable with respect to the insert 14 with some force. Thus, a tight,non-floppy ball and socket joint is now created between the insert 14and the shank upper portion 8 as well as between the retainer inner andouter surfaces and adjacent surfaces of the shank head 8 and thereceiver seating surface 100. At this time, the receiver 10 and may bearticulated to a desired angular position with respect to the shank 4,such as that shown in FIGS. 36 and 37, but prior to insertion of the rodor closure top, that will be held, but not locked, by the frictionalengagement between the retainer 12, the shank upper portion 8 and thereceiver 10. With reference to FIG. 36, angular pivoting or articulationof the shank 4 with respect to the retainer 12 is shown. With referenceto FIG. 37, angular pivoting or articulation of the retainer 12 withrespect to the receiver 10 is shown as well as articulation of the shank4 with respect to the retainer 12.

With reference to FIG. 38, the rod 21 is eventually positioned in anopen or percutaneous manner in cooperation with the at least two bonescrew assemblies 1. The closure structure 18 is then inserted into andadvanced between the arms 62 of each of the receivers 10. The closurestructure 18 is rotated, using a tool engaged with the inner drive 186until a selected pressure is reached at which point the rod 21 engagesthe U-shaped seating surface 142 of the compression insert 14, pressingthe insert surface 168 into locked frictional engagement with the shankspherical surface 34. Specifically, as the closure structure 18 rotatesand moves downwardly into the respective receiver 10, the rim 190engages and penetrates the rod surface 22, the closure structure 18pressing downwardly against and biasing the rod 21 into compressiveengagement with the insert 14 that urges the shank upper portion 8toward the retainer 12 and into locking engagement therewith, theretainer 12 frictionally abutting and expanding outwardly against thespherical surface 100. For example, about 80 to about 120 inch pounds oftorque on the closure top may be applied for fixing the bone screw shank4 with respect to the receiver 10.

An alternative lock-and-release compression insert (not shown) may beidentical or substantially similar to the insert 14 previously describedherein, with the exception that the locking insert is sized for africtional interference fit with the receiver 10; specifically, alocking interference between the cylindrical inner surface 90 of thereceiver 10 and a part or portion of the outer body surface 143 that issized and shaped to have a greater diameter than the diameter of theillustrated surface 143. Such a locking insert would preferably furtherinclude a pair of opposed through bores extending through the insert armsurfaces or some other feature for receiving tooling for unlocking ofsuch insert from the receiver. Such an insert may be assembled with thereceiver 10, retainer 12, shank 4, rod 21 and closure top 18, in amanner the same as previously described above with respect to theassembly 1, with the exception that the alternative insert would beforced downwardly into a locking interference fit with the receiver 10when the shank 4 is locked in place, as compared to the easily slidingrelationship between the insert 14 and the receiver 10. One way in whichto force the alternative insert into locking interference is by assemblywith the rod and closure top. After being fully locked down, the closuretop may be loosened or removed and/or the rod may be adjusted and/orremoved and the frictional engagement between the alternative insert andthe receiver 10 at the interferingly fixed surfaces would remain inplace, advantageously maintaining a locked angular position of the shank4 with respect to the receiver 10. At this time, another rod, such as adeformable rod and cooperating alternative closure top may be loadedonto the already locked-up assembly to result in an alternativeassembly. The drive of such a closure top may advantageously be madesmaller than the drive of the closure 18, such that the deformable rodis not unduly pressed or deformed during assembly since the polyaxialmechanism is already locked.

With reference to FIG. 35, a temporary locking and manipulation tool,generally 700, is illustrated in phantom for independently, temporarilylocking the insert 14 against the shank head 8 and thus temporarilylocking the angle of the shank 4 with respect to the receiver 10. Thetool 700 includes a pair of opposed arms 712, each having an engagementextension 716 positioned at an angle with respect to the respective arm712 such that when the tool is moved downwardly toward the receiver, oneor more inner surfaces 718 of the engagement extension 716 slide alongthe surfaces 77 of the receiver and along the surfaces 157 of the insert14 to engage the insert 14, with a surface 720 pressing downwardly onthe insert surfaces 158, pushing the insert downwardly and pressing thespherical surface 168 into locking frictional fit with the sphericalsurface 34 of the shank 4. It is foreseen that the tool 700 may includea variety of holding and pushing/pulling mechanisms, such as a pistolgrip tool, that may include a ratchet feature, a hinged tool, or, arotatably threaded device, for example for temporarily holding or fixingthe polyaxial mechanism of the assembly 1 in a desired position ororientation.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. In a bone anchor, the improvement comprising: a) a shankhaving a body for fixation to a bone and an integral upper portionhaving a substantially spherical surface; b) a receiver having a topportion and a base with a lower opening, the receiver top portiondefining a first open channel, the base having a curved surfacepartially defining a cavity, the channel communicating with the cavityand the lower opening; c) at least one insert disposed within thereceiver, the insert having a second open channel and a concave surfaceoperatively frictionally mating and locking with the shank firstspherical surface; d) a resilient open retainer captured within thecavity and expandable in the cavity about at least a portion of theshank, the open retainer having an inner surface for unlocked slidable,articulatable engagement with the shank and an outer surface forunlocked slidable articulatable engagement with the receiver curvedsurface; and e) wherein expansion-only operative locking engagementoccurs between the shank upper portion and the retainer and between theretainer and the receiver.
 2. The improvement of claim 1 wherein thereceiver curved surface has a first radius and the retainer outersurface has a second radius, the first radius being substantially equalto the second radius.
 3. The improvement of claim 1 wherein the retainerinner surface has a first radius and the shank substantially sphericalsurface has a second radius, the first radius being substantially equalto the second radius.
 4. The improvement of claim 1 wherein at least oneof the insert arms has an outer surface engaging the receiver topportion.
 5. The improvement of claim 4 wherein the receiver top portionhas at least one surface crimped inwardly against at least one of theinsert arms.
 6. The improvement of claim 1 wherein the insert is toploaded into the receiver and then rotated into a position above theretainer with the second channel aligned with the first channel.
 7. Theimprovement of claim 1 wherein the receiver top portion has a first pairof opposed tool receiving through apertures formed therein and theinsert has a second pair of opposed tool receiving apertures inalignment with the first pair of apertures, the first pair of aperturessized and shaped to provide tool access to the insert, each of thesecond pair of opposed tool receiving apertures having a tool receivingsurface sized and shaped to allow a tool to press the insert downwardlyinto temporary locking engagement with the shank.
 8. The improvement ofclaim 7, wherein the receiver top portion has at least one slopingsurface communicating with each of the first pair of apertures, eachsloping surface sized and shaped for aligning a tool with the respectiveinsert tool receiving surface.
 9. The improvement of claim 8 wherein thereceiver top portion at least one sloping surface is a first slopingsurface and the insert has a second sloping surface substantiallyaligned with the first sloping surface, the second sloping surface beingadjacent to and oriented at an obtuse angle with respect to one of theinsert tool receiving surfaces.
 10. The improvement of claim 1 whereinthe retainer has a top surface and a slit.
 11. The improvement of claim10 wherein the slit is disposed at an obtuse angle with respect to thetop surface.
 12. The improvement of claim 10 wherein the retainer topsurface is planar.
 13. The improvement of claim 1 wherein the insert isspaced from the retainer in all angular orientations of the shank withrespect to the receiver.
 14. In a bone anchor, the improvementcomprising: a) a shank having a body for fixation to a bone and anintegral head having at least one curved surface; b) a receiver having atop portion and a base, the receiver top portion defining an openchannel, the base having a first surface partially defining a cavity,the channel communicating with the cavity, the receiver having at leastone tool receiving through aperture; c) at least one insert disposedwithin the receiver, the insert sized and shaped to directly engage withthe shank head curved surface and to cooperate with lock and releasetools that extend through the receiver tool receiving aperture forpressing the insert downwardly against the shank head into one ofnon-floppy sliding engagement and temporary locking engagement with theshank head; and d) a resilient open retainer captured within the cavityand expandable within the cavity about at least a portion of the shankhead, the retainer having a first polyaxial articulation with the shankhead and a second polyaxial articulation with the receiver when in anunlocked position, and wherein expansion-only locking engagement occursbetween the shank head and the retainer and between the retainer and thereceiver when in a locked position.
 15. The improvement of claim 14wherein the at least one tool receiving aperture is a pair of opposedtool receiving apertures and the insert has a pair of opposed recessedtool receiving surfaces formed in outer walls thereof, the recessed toolreceiving surfaces being accessible through the receiver tool receivingapertures.
 16. The improvement of claim 14 wherein the receiver has afirst tool receiving sloping surface adjacent the through aperture andthe insert has a second tool receiving surface generally aligned withthe first tool receiving sloping surface.
 17. The improvement of claim16 wherein the insert tool receiving surface forms a v-shaped recess.18. In a bone anchor, the improvement comprising: a) a shank having abody for fixation to a bone and an integral head having a firstspherical surface; b) a receiver having a top portion and a base, thereceiver top portion having first and second opposed arms defining anopen channel, the base having a lower opening and a second sphericalsurface partially defining a base cavity, the channel communicating withthe cavity and the lower opening, each receiver arm having a toolreceiving sloping surface and a through aperture; c) at least one toploaded insert disposed within the receiver, the insert having a thirdspherical surface sized and shaped to directly engage with the shankhead first spherical surface, the insert having third and fourth opposedarms, each arm having a recessed surface aligned with one of thereceiver sloping surfaces and sized and shaped for receiving lock andrelease tools that extend through the receiver tool receiving aperturesfor pressing the insert downwardly into engagement with the shank head;and d) a resilient open retainer captured within the cavity andexpandable within the cavity about at least a portion of the shank headfirst spherical surface, the retainer having a first polyaxialarticulation with the shank head first spherical surface and a secondpolyaxial articulation with the receiver second spherical surface whenin an unlocked position, and wherein the retainer is in expansion-onlylocking engagement between the shank head and the receiver when theshank is in a locked position with respect to the receiver.
 19. Theimprovement of claim 18, wherein the retainer has a fourth sphericalsurface and a fifth spherical surface, the fourth spherical surfaceengaging the shank first spherical surface and the fifth sphericalsurface engaging the receiver second spherical surface.
 20. Theimprovement of claim 18, wherein the insert is top loaded into thereceiver.